The historical evolution of the natural sciences, from natural history to specialized scientific disciplines, has fundamentally altered how we study the natural world. While scientific specialization has undoubtedly brought both depth and rigor to specific scientific fields, including primatology, it has also created methodological limitations that fragment our understanding of complex primate ecosystems. This paper outlines four core principles, once central to natural history research, that are less commonly applied in contemporary primatology. These principles include: multidisciplinarity, democratized participation, integration of subjective interpretation, and creative communication. I argue for the strategic integration and/or reintegration of these principles within primatology and provide concrete recommendations for institutional enactment. However, while the incorporation of these selected principles may make the field more inclusive, ethical, and diverse, it is critical to also acknowledge that many other aspects of natural history have been historically rooted in a colonialism, racism, and exploitation. This paper, therefore, does not call for a blind return to natural history approaches as they were once practiced, but rather for the development of a new, holistic, next-generation primatology. Rather than abandoning scientific rigor, this synthesis approach would expand primatology's methodological toolkit to better reflect the interconnected nature of primate worlds while bridging the gap between academic and local knowledge systems. Such integration offers pathways toward more inclusive, comprehensive, and ultimately more effective primate research and conservation.
The distribution of African great apes has remained unconfirmed regarding their southern limit, particularly on the western side of the continent. IUCN maps include the Mayombe forest of Angola as part of the estimated distribution of western lowland gorillas (Gorilla gorilla gorilla) and central chimpanzees (Pan troglodytes troglodytes). However, until now, there were no records confirming the continued presence of both species. The Mayombe forest is a key biodiversity hotspot and a potentially important stronghold for the conservation of great ape populations in Africa. Here, we report the first systematic evidence of both species in the Mayombe National Park, Cabinda, Angola. In 2023, a grid of camera traps was systematically deployed, producing the first visual records of gorillas and chimpanzees. Building on these findings, in 2024, a pilot survey including ad libitum field observations was carried out along exploratory trails to maximise data collection. The combination of these records identified a hotspot of great ape activity where six transects were established, and systematic direct and indirect evidence was documented. Chimpanzees were recorded more times across a broader range of evidence categories, while gorillas appeared less and seemed more spatially restricted. Notably, both species were detected at overlapping sites but never simultaneously, indicating sympatric coexistence with spatio-temporal partitioning. These findings confirm the southernmost predicted distribution of both species for this part of Africa, filling critical gaps in the understanding of great ape evolution and biogeography, and providing a baseline for the first demographic and ecological census of great apes in Angola.
We describe and name a new species of African monkey, Colobus congoensis sp. nov. (Primates, Cercopithecidae), from the interfluve region of the Lomami and Congo (Lualaba) Rivers in east-central Democratic Republic of Congo (DRC). Colobus congoensis is a rare and cryptic monkey, poorly known even by local communities bordering its range, some of whom use the vernacular name Likweli for the species. Between 2018 and 2022, 114 field observations were made over an estimated range of 1,700 km2. Colobus congoensis is largely restricted to high, closed canopy forest on deep clay pediments and islands of terra firme forest, where it co-occurs with two other colobine species (Piliocolobus parmentieri and Colobus angolensis). Colobus congoensis was most frequently observed in small groups (mean = 6.2 individuals), often in mixed-species associations. Mitochondrial and morphological data confirm the attribution of C. congoensis to the genus Colobus and reveal that it is the sister to Colobus satanas, from which it is geographically separated by more than 1,200 km. Comparative analysis of C. congoensis vocalizations also reveals structural similarities with C. satanas to the exclusion of other Colobus species. Among other features, C. congoensis is distinguished from C. satanas and other Colobus species by its small size, a striking orange cream patch surrounding the mouth, philtrum, and portions of the inferior nasal alae on an otherwise black face, and a white perianal patch that is covered with fine white hairs in males and is glabrous in females. We propose a preliminary IUCN Red List classification of Endangered (EN) for C. congoensis based on its small range area and population size, coupled with the projected impact of increased hunting pressure and habitat conversion. Protection of Lomami National Park, within which most of the C. congoensis range occurs, and engagement of local communities in not hunting the species are the most important actions needed to ensure the conservation of C. congoensis.
Only a few records of pigmentation anomalies, particularly hypopigmentation conditions such as albinism, have been reported among Neotropical non-human primates. In Brazil, there are only 14 documented cases of pigmentation anomalies, with just two instances of albinism recorded within the Cebidae family. To our knowledge, no pigmentation polymorphisms have been documented in the Pitheciidae family to date. In this study, we report the first documented case of albinism in Callicebus nigrifrons (the black-fronted titi monkey) within the largest remnant of the Atlantic Forest in the State of Minas Gerais, Brazil. This observation was made using a drone equipped with 4K cameras and thermal infrared sensors. This primate exhibited characteristics such as the absence of pigmentation in its fur, as well as in its palms of its hands and feet, and dark red eyes. It was observed in a group composed of two other individuals displaying typical coloration. The group's behavior was normal, showing no signs of exclusion toward the albino individual. Potential causes of albinism in C. nigrifrons may include genetic or environmental factors, or combined pressures, though these remain speculative. This is the first confirmed case of albinism in the Pitheciidae family and the first record of such a phenomenon using drone technology in the wild. Our findings underscore the potential of drones for detecting low-frequency phenotypic traits in elusive species and reinforce the role of protected areas such as the Rio Doce State Park in safeguarding threatened and genetically distinct individuals.
Today's students are tomorrow's leading scholars. With effective mentoring, they will continue to address key issues in the critical work that will conserve and protect our closest living relatives-our fellow primates. The articles presented as part of this special issue on student-led work in primatology reflect the tremendous breadth of the field, covering such broad topics as diet, reproduction, conservation, husbandry, physiology, social behavior, welfare, and cognition. These studies were conducted in both field and captive settings, reflecting the diversity of contexts in which primates are being actively studied today. Whereas some of the work focuses on basic research questions, all of the papers have the potential to impact the lives of primates today and into the uncertain future. We hope that cultivating this collection of student-led work will highlight the fertility and importance of work in this field and inspire established researchers to continue to invest in mentoring the next generation of scientists.
Diurnal primates show periods of wakefulness at night because of ecological factors, but the degree to which they shift the timing of their activities in response to anthropogenic factors is poorly understood. We aimed to examine whether Geoffroy's spider monkeys (Ateles geoffroyi) are active during the night and evaluate the effects of climatic and anthropogenic factors on their nocturnal activity. We conducted 66 half-night behavioral observations on wild spider monkeys at a known sleeping site in the human-modified habitat of Los Árboles Tulum, Quintana Roo, Mexico between August 2018 and July 2019. We used generalized linear mixed models to test the effects of moonlight intensity, heat index, anthropogenic light, and anthropogenic noise on vocal and non-vocal activity during the night. Diurnal spider monkeys showed some level of activity at all hours of the night within their sleeping site. We found no effect of the predictor variables on the amount of time spider monkeys were non-vocally active, but the number of vocalizations was positively affected by moonlight intensity, heat index, and anthropogenic noise, and negatively by anthropogenic light. Increased moonlight intensity, perceived temperature and noise may disrupt sleeping patterns, leading to more vocal activity, whereas spider monkeys may emit whinnies when they cannot see one another, potentially explaining the negative relationship between the number of whinnies and anthropogenic light. Our findings contribute to the view that diurnal primates may be more flexible in their activity patterns than previously thought and that spider monkeys can adjust to permanent low-level anthropogenic impact and live alongside humans in modified habitats.
Winners of aggressive intergroup encounters are often assumed to benefit from increased access to resources, but few studies have measured whether there is differential access to resources based on the intergroup outcome. To investigate whether winning intergroup encounters is associated with increased access to food, we used 13 months of data on intergroup dynamics, feeding by 61 females, and the phenology and spatial distributions of food trees from the home ranges of 8 groups of white-thighed black-and-white colobus (Colobus vellerosus) at Boabeng-Fiema, Ghana. Contested trees were important food species more often than expected based on the occurrence of these species in the study area. Contested trees had young leaves, fruits, and seeds more often than expected based on the presence of these plant parts on trees monitored via monthly phenology surveys. Focal females were more likely to feed on the contested tree than other trees they were in during and immediately after the intergroup encounter. Based on group scan data collected throughout the day of an intergroup encounter, the likelihood of females feeding on any food species before and during the intergroup encounter was similar regardless of the outcome. The likelihood of feeding was higher after the intergroup encounter if the group had won compared to if the group had lost. These findings indicate that groups compete over access to important food resources and winners benefit from increased access to food. Future studies should investigate whether winning intergroup encounters is associated with long-term benefits such as increased reproductive success.
The phenology of trees in tropical forests shapes the temporal distribution of resources such as fruits and leaves. In montane forests (> 1000 m altitude), tree diversity and primary productivity tend to decline with elevation, correlating with lower temperatures and resulting in low food availability for herbivorous and frugivorous consumers. In such environments, wild animals often rely on adaptive food choice strategies to cope when preferred resources are scarce, shifting to less preferred but more available items. This research examines the feeding strategy of red howler monkeys (Alouatta seniculus) inhabiting a montane forest in the Colombian Andes (2,500-3,000 m asl) by analyzing their food intake (grams of dry weight) and their response to resource availability and food species aggregation over an annual cycle. We recorded 1,277 h of continuous focal animal sampling of two howler groups and monitored 28 phenological plots within their home range. Fruit availability varied throughout the year, with asynchronous fruiting patterns observed both within and between species, while leaves remained available all year-round. Montane howlers maintained a predominantly folivorous diet; however, only the daily intake of young leaves and ripe fruits was significantly explained by their availability. Overall, total daily food intake increased with ripe fruit and flower availability but decreased with that of unripe fruits, even though did not explain ripe fruit consumption. In contrast, the aggregation of food species had no effect on daily food intake. Although availability varied among items, montane howler monkeys adjusted their consumption patterns to specific resources availability (e.g., increasing intake of ripe fruits and young leaves during periods of higher availability), within the context of their primarily folivorous feeding strategy.
The co-occurrence of species within the same area raises fundamental questions about how they can persist while sharing space and resources. One of the central aims of community ecology is to understand the processes that allow species to coexist over time. The sympatry between primates and ungulates has not received much specialized attention, despite long-term acknowledgment that the two groups frequently co-occur. In this contribution, we have reviewed and summarized empirical evidence from a set of published studies to determine the nature of primate and ungulate association in space and time, the ecological contexts within which such associations occur, and the types of interactions that have been reported. We particularly examined the trends in the study taxa, the geographic distribution of research, and the functional categories of interactions. Within the literature, interspecific interactions are frequently reported in Africa, between baboons (Papio sp.) and small to medium-sized ungulates. Foraging facilitation and antipredator benefits are among the most frequently documented interaction types, typically resulting in commensalistic or asymmetrical mutualistic outcomes favouring ungulate species. Nonetheless, mutualism and antagonistic interactions are also reported, which indicates the context-dependent nature of these relationships. The frequency and form of associations appear to further depend on seasonal variation and habitat structure, although these factors were not consistently taken into account in the studies considered in this review. This synthesis helps establish a set of research priorities to promote more systematic and focused studies of primate-ungulate sympatry.
Environmental changes, such as transfers and social introductions, can be major sources of stress in wild animals. Monitoring the physiological response through glucocorticoids is an effective tool to assess how animals cope with and adjust to these changes. In this study, we followed the habituation and social integration of Suzie, a former pet and entertainment chimpanzee confiscated and transferred to a primate rescue center. Our objectives were to (1) monitor her fecal glucocorticoid metabolite (FGM) levels throughout rehabilitation, and (2) investigate how association-related factors (e.g. number of individuals, ages of association partners) influenced her FGM levels and social behaviors during associations with the resident chimpanzees. A total of 169 fecal samples from Suzie were collected over 10 months and quantified using enzyme immunoassay, along with 38 opportunistic samples from the resident chimpanzees. During association sessions, data on aggressive and affiliative events were recorded. Suzie's FGM levels ranged from 11.01 to 113.04 ng/g of feces. After a four-month adjustment period (118 days) before returning to basal hormone activity, her FGM concentrations aligned with individual mean levels of the resident chimpanzees (range: 24.19 ± 7.99 to 29.69 ± 8.93 ng/g of feces). The presence of a broker individual during associations impacted the likelihood of affiliative events (p < 0.01). Furthermore, early social housing conditions of the resident chimpanzees influenced social dynamics, with affiliative behaviors being more likely to occur while interacting with individuals who were housed in social groups during infancy, and aggressive events being more likely to occur while interacting with those housed alone (p < 0.05). Our findings underscore the value of non-invasive hormone monitoring and behavioral assessments to better understand individual experiences.
While most scholars across the social and biological sciences acknowledge that human culture is distinctive in the comparative context there is widespread acknowledgment that some form of culture does occur in other animals, including in many species of primates. Here we outline key historical patterns and the changes in primatology and the behavioural sciences regarding the concepts of primate culture. In the contemporary moment new methods and approaches are emerging as the field of inquiry matures. Our assessment is that continued and expanded inclusion of methods and theory from both the social and the natural sciences is beneficial, and that a further development of a form of primate ethnology for the comparison and analysis of primate cultures is needed. With a better understanding of the complexities of the primate cultural dynamic, scientists may better be able to model their evolutionary dynamics and consider aspects of primate cultures in conservation action.
Once thought to be uniquely human, tool use is now recognized in a range of non-human animals, with non-human primates frequently using tools in foraging contexts. Stone tool use is a common behavior in different species of capuchin monkeys, with evidence of behavioral and cultural differences across populations. In this study, we document stone tool use during percussive foraging in a previously unstudied population of capuchin monkeys at the Monkeyland Primate Sanctuary, South Africa. Of 87 mapped nut‑cracking sites, 77 yielded behavioral data comprising 1,359 recorded bouts. Capuchins showed a strong preference for organic anvils (roots n = 1,161, trunks n = 173, branches n = 23; with only 2 bouts on stone anvils) and used a wide range of hammer masses (25-1,581 g). Average nut‑cracking success was ~ 75%. Results show that nut-cracking success varies depending on both the capuchins' preferred hand and the size of the hammer they use. Additionally, we found strong individual differences in hand preference, which suggests that Monkeyland capuchins can adapt their techniques to improve their success. Because observations were limited to a subset of identified individuals between May andAugust, sex‑bias results are preliminary and future year‑round sampling is needed. Overall, our study adds to the growing body of research on capuchin cultural diversity by documenting tool use in a previously unstudied semi-free-ranging population. This preliminary assessment demonstrates the value of Monkeyland as a primate archaeology research site that preserves key ecological and social conditions while offering a unique balance between naturalistic behaviors and research accessibility.
The Upper Guinean forests of West Africa are a major global hotspot for primate diversity, yet many areas remain understudied and insufficiently protected. Southeastern Côte d'Ivoire illustrates this conservation gap. Once home to several of West Africa's most threatened primate species, the region has experienced extensive deforestation, habitat fragmentation, and hunting pressure over recent decades. Consequently, many primate populations have declined or disappeared from large parts of their former range. The Tanoé-Ehy Forest, a swamp forest ecosystem located along the Côte d'Ivoire-Ghana border, is now one of the last refuges for several endangered primates in the region. Since 2006, a long-term conservation initiative led by Ivorian scientists, in partnership with local communities, has aimed to protect this forest and its biodiversity through a community-based conservation approach. This article presents the Tanoé-Ehy conservation initiative as a case study demonstrating how locally led conservation efforts can support both biodiversity protection and community empowerment while contributing to changes in conservation practice in African primatology. Over nearly two decades, the project has combined ecological research, participatory governance, and socio-economic initiatives. Community members actively participate in wildlife monitoring, forest surveillance, environmental education, and livelihood diversification programs designed to reduce pressure on forest resources. Beyond biodiversity protection, the initiative highlights the importance of strengthening national scientific leadership and recognizing local communities as central actors in conservation governance. The Tanoé-Ehy experience shows that effective and sustainable conservation in biodiversity-rich regions depends on integrating local knowledge, equitable partnerships, and long-term community engagement.
Traumatic injuries are a major cause of morbidity and mortality in free-ranging non-human primates (NHPs), often associated with anthropogenic pressures such as habitat loss, urbanization, and interactions with domestic animals. This study characterized some epidemiological, spatial, and pathological patterns of mechanical traumatic injuries in free-ranging non-human primates from anthropogenically altered areas of the Federal District. Of 696 necropsies performed, 215 cases (30.9%) involved mechanical trauma. Black-tufted marmosets (Callithrix penicillata) were the most affected species (90.2%), followed by capuchins (Sapajus libidinosus, 6.5%) and howler monkeys (Alouatta caraya, 3.3%). Adults were more frequently affected than juveniles, with no sex-related differences. Blunt trauma accounted for the majority of cases (82.3%), most commonly as polytrauma, with cranial involvement in 65.2% of animals. Carnivore predation was the leading cause of blunt-penetrating trauma (89.4%), while gunshot injuries were rare. Bone fractures were identified in 65.1% of cases, most often involving the skull and long bones, and internal injuries were frequent in the thoracic and abdominal cavities. These findings demonstrate that mechanical trauma represents a critical threat to NHPs in urban and peri-urban areas, where exposure to human infrastructure and domestic animals is heightened. The results underscore the need for mitigation strategies to reduce mortality and support the conservation of free-ranging primate populations in human-dominated landscapes.
The genes of the major histocompatibility complex (MHC) are vital to vertebrate immunity and may influence mate choice in several species. The extent to which the MHC influences female mate choice in primates remains poorly understood, and studies of MHC-based mate choice in platyrrhines are especially rare. White-faced capuchin monkeys (Cebus imitator) reside in multimale-multifemale groups where alpha males sire most of the offspring, but females related to the alpha male reproduce with subordinate males. In this study, we investigated the potential role of MHC genotypes, in the context of social dominance and relatedness, in determining which mating pairs produced offspring in wild white-faced capuchins in the Sector Santa Rosa, Área de Conservación Guanacaste, Costa Rica. We found that neither the social status nor the siring success of males was associated with their MHC metrics. Using mixed conditional logit models and generalized linear models, we found that MHC metrics did not predict the probability of siring offspring or being an alpha male. Alpha males that were distantly related to reproducing females were significantly more likely to sire offspring regardless of MHC genotype. However, we did find some evidence that subordinate males heterozygous at MHC loci sired significantly more offspring than homozygous subordinate males. Further, one-sided binomial simulations revealed that offspring were more frequently heterozygous at MHC loci than expected given the gene pool. We conclude that in this population, females related to the alpha may preferentially mate with MHC-diverse subordinate males, leading to increased probabilities of MHC-diverse offspring.
Studying nonhuman primates' responses to the death of conspecifics has gained growing interest in comparative thanatology providing wider evolutionary context for our understanding of human responses to death and mourning. Primates exhibit diverse reactions to infant deaths, with infant corpse carrying (ICC) being most frequently reported. We tested existing hypotheses about the functional significance of ICC and describe other behaviors directed towards corpses using 21.7 years of observations on mountain gorillas involving 141 infant deaths. ICC is common in mountain gorilla mothers (60.5% of deaths) with an average duration of 4.9 days. Consistent with primate literature, ICC by mothers occurred less often and for shorter durations after traumatic deaths and with increasing infant age at death. Mothers' parity, season, and whether a mother had previously carried an infant corpse did not affect ICC. Non-mothers across age classes and sexes participated in ICC and directed affiliative and investigative behaviors toward corpses, reflecting the important role that non-mother caregivers can play in infant gorillas' development and survival. Nulliparous and primiparous females were proportionally more often non-mother carriers than multiparous females which supports the 'learning to mother' hypothesis. Our findings suggest that delays in overcoming strong attachment bonds and difficulties in detecting death lead to a greater likelihood and longer duration of carrying after death. Understanding these behaviors in mountain gorillas enriches our knowledge of their social and care systems and contributes to broader discussions on primate cognition and responses to death.
Obesity is an often-stated issue in zoo animals, including primates, and has historically been particularly emphasized for lemurs. By contrast, similar reports for colobine species-which are literally called 'slim monkeys' in at least one other language-are absent. This has been hypothsized to be linked to the colobine foregut fermentation system; diets high in easily digestible carbohydrates might disturb the microbiome in the foregut, similar to acidosis in domestic ruminants, leading to reduced intake and disease rather than obesity, but empirical data is lacking. We compared body mass (BM) data for 14 lemur species (7187 individuals) and 10 colobine species (1443 individuals) with literature data on free-ranging specimens to test this concept. In contrast to expectations, a similar percentage of species had a majority of individuals above the 'healthy' BM range in at least one sex (36% of lemur and 40% of colobine species). However, colobines had a higher percentage of individuals considered 'underweight', especially in the two rarely kept species with the more complex 'quadripartite' stomachs (Nasalis larvatus, Pygathrix nemaeus). Neither sample size, sexual size dimorphism, the degree of folivory, nor indications for a seasonal physiology were clearly associated with species' propensity for zoo obesity. There were no clear historical trends in the development of obesity in these species. We conclude that no general rules about species' susceptibility to obesity appear to apply. Body mass and condition of zoo primates should be monitored continuously, and feeding regimes possibly be adapted to contain diets of higher fibre levels more similar to those reported in natural diets.
The howler monkeys (Alouatta) are part of the Platyrrhini infraorder, a group of Neotropical primates with the widest geographical distribution, occurring from southern Mexico to northern Argentina. Previous phylogenetic studies based on cytogenetic, morphological, and molecular data have shown inconsistent results, requiring new approaches to clarify relationships within the genus. In this study, we analyzed nine species of Alouatta using 24 molecular markers (2 mitochondrial and 22 nuclear genes). Through Bayesian inference, Maximum Likelihood, and divergence time analyses, we inferred the phylogeny and estimated the timing of speciation events. Our results recovered two major clades within Alouatta, corresponding to Mesoamerican (Trans-Andean) and South American (Cis-Andean) lineages. Most diversification events occurred during the Pliocene. Within the South American clade, we identified two well-supported groups: one composed of species from the Atlantic Forest and eastern Amazon (A. guariba, A. belzebul, and A. discolor), likely shaped by the formation of the South American dry diagonal; and another formed by A. caraya and the A. seniculus complex. Notably, our results confirmed a close phylogenetic relationship between A. discolor and A. belzebul, and between A. macconnelli and A. nigerrima, which occur on opposite sides of the Amazon River.These relationships, along with the confirmation of A. discolor and A. nigerrima as distinct species based on multilocus evidence from known localities, represent advances over previous studies and contribute to a more resolved understanding of Alouatta diversification.
Primate research has long depended on the deep ecological and behavioral knowledge of local communities living near or within primate habitats, yet this knowledge has rarely been given the same visibility as academic science. In this collaboratively formulated article we argue that including local and traditional knowledge alongside scientific studies enriches primatology epistemically, ethically, and practically. We introduce the Perspectives Collective Journal, a collaborative multimedia journal-the first of its kind-created to support the direct sharing of local and traditional insights about primates, as well as other species, in their natural habitats. By providing an accessible and flexible platform for storytelling, reflection, and documentation, including written articles, participatory films, interviews, and group discussions, Perspectives invites a plurality of voices and formats into primatological knowledge production. Here we highlight several ways in which local knowledge can contribute to primatology and its complementary relationship to mainstream science by drawing upon materials published in Perspectives and framing it in relation to the mainstream scientific literature on primate behavior. Overall, this paper and the Perspectives project more generally demonstrate the value of allowing diverse knowledge systems to meet on equal footing.
Vocal communication is a critical aspect of social life in group living species. Ring-tailed lemurs (Lemur catta) are one of the most studied lemur species, yet the quantity of male specific vocalizations remains unclear. Howling has previously been described as a male only vocalization. While investigating Duke Lemur Center (DLC: Durham, N.C.) ring-tailed lemurs' responses to novel objects when separated from their group for five minutes, video and audio opportunistically captured a female howling. We sought to determine whether these vocalizations were acoustically similar to male howling or represented a different vocalization. We focused on body posture and acoustic structure of the call by analyzing spectrograms of the female's calls, and compared these features to male howls. Body posture comparison revealed similarities in the female's position and orientation of the body to males when howling. From the spectrograms, we compared the fundamental, maximum, maximum harmonic, dominant, supradominant frequencies, interharmonic intervals, and number of harmonics to values extracted from the published literature. A linear discriminant function analysis (DFA) failed to distinguish the female's calls from male howls. This is the first recording and analysis of female howling vocalizations. While male ring-tailed lemurs are known to howl to advertise their location, it's possible that female lemurs may howl for different reasons. Females may howl during high stress events, and we suggest future research to understand the conditions that elicit howling vocalizations in females in the wild and in captivity.